"The Walking Dead" closed out the first half of Season 3 the same way it started it: breaking ratings records.A total 15.2 million viewers watched the "Walking" midseason finale episode over three airings on AMC last night (Dec. 2). That includes 10.5 million during the 9 p.m. premiere airing, a 58% increase over the Season 2 midseason finale (which was already doing great by cable standards).According to AMC, the ratings momentum makes "Walking Dead" the "first cable series in television history" to rank as the #1 fall TV entertainment series in the key 18-49 demographic. That means "Walking" outdid all broadcast rivals in the demo including heavyweights like "The Voice," "Modern Family" and "The Big Bang Theory."Adding to the cable network's good news, the midseason finale of "Talking Dead" drew 2.2 million viewers at 11 p.m. following the first encore airing of "Walking." That's a 110% increase from the comparable episode last year.As previously announced,...